H-guide hybrid junction having an elongated coupling slot



Nov. 1, 1966 BIRENBAUM ETAL 3,283,266

H-GUIDE HYBRID JUNCTION HAVING AN ELONGATED COUPLING SLOT Filed Dec. 30, 1963 INVENTORS LEO BIRENBAUM BY JOHN,W.E.GRIEMMANN an (r //CZCI"I)L 7 Z Qg J ATTORNEYS United States Patent 3,283,266 H-GUIDE HYBRID JUNCTION HAVING AN ELONGATED COUPLING SLOT Leo Bireubaum, New York, and John W. E. Griemsmann, Queens Village, N.Y., assignors to Polytechnic Institute of Brooklyn, Brooklyn, N.Y., a corporation of New York Filed Dec. 30, 1963, Ser. No. 334,127 4 Claims. (Cl. 317-249) This invention relates to hybrid junctions in electric waveguides of the H-guide type.

In particular, the invention is concerned with a coupling arrangement between two sections of Waveguides of the H-guide type, to produce a 4-port hybrid junction in which when energy is introduced into one port, it is transmitted through the coupling and is divided and passes out of the two ports of the other H-guide section in equal amounts.

An object of the invention is to devise an H-guide hybrid junction of broadband characteristic, and of relatively simple construction.

Another object is to devise an H-guide hybrid junction in which the two waveguide sections are coupled together by a single slot in a common wall between the two sections.

A suitable embodiment of the invention is illustrated in FIGURE 1 which shows the arrangement in perspective, with certain parts being broken away to illustrate the internal construction; and FIGURE 2 is a sectional view of FIGURE 1 taken along the cutting plane 2-2 and illustrating the construction at the location of the coupling slot between the two H-guide sections.

As shown in FIGURE 1, the hybrid junction is formed of two H-gui=de sections and 11 arranged in a generally parallel relation. Section 10 is provided with ports A and B at the ends thereof, while section 11 is provided with ports C and D at its ends.

Each H-guide section is formed in three linear sections, such as end sections 10a and 10b and middle section 10c for section 10, and end sections 11a and 11b and middle section 110 for section 11. The end section 10a is formed of two conductive strips or plates 10a and 10a" held in parallel relation by suitable spacing means located at the outer edges thereof, such as the spacers 12 distributed along the length of the strips. In a like manner, the section 10b is formed of two conductive strips or plates 10b and 10]) held in spaced parallel relation by the spacers 12. Coupling flanges Fa are provided at the ends of conductive strip 10a, and coupling flanges Fb are provided at the ends of conductive strip 10b.

The central section 100 of H-guide section 10 is formed of a rigid conductive flat plate 10c extending between coupling flanges Fa and Fb and is coupled to these flanges by cooperating flanges Fe and F0 secured to the two ends of the plate 100. It will be understood that the inner surface of the plate 100' effectively is a continuation of the inner surfaces of plates 10a and 10b.

The H-guide section 11 is constructed of three linear sections in the same manner as the H-guide section 10, the arrangement being symmetrical about a plane passing midway between the two mid-section plates 10c and 110', the end sections 11a and 1112 being formed respectively of parallel conductive strips or plates 11a, 11b and 11a", 11b" held in spaced parallelrelation by suitable spacers 12. The mid-section 11c is also formed in an identical manner as the mid-section 10c.

As shown in FIGURE 1, the two waveguide sections at the ends containing ports A and D are spaced apart and held in spaced relation by a common coupling flange 13a, but they converge at the other end and the inner conductive strips 10a" and 10b" come together and merge into "ice a single strip at the plane between the coupling flanges Pa and Fe. Likewise, the two H-guide sections at the ends containing ports C and B are spaced apart and held together by a common coupling flange 13b. The two waveguide sections converge from the flange 13b so that the inner strips 10b and 11b come together and merge into a single wall in the plane of the coupling flanges Pb and Fe. A single flat aperture plate 14 is supported midway between the mid-section plates 10c and this plate constitutes a continuation of the merged ends of plates 10a" and 10b" of section 10a and the merged ends of plates 10b" and 11b" of section 10b.

In accordance with the usual construction of an H- guide, a strip of dielectric material 15 is located between the conductive plates of the H-guide section 11 and extends along the middle of these plates from one port A to port B. Likewise, a dielectric strip 16 extends between the port C and the port D of the section 11. A suitable material is a dielectric foam known by the name polyfoam. The two conductive strips of each H-guide section are sufliciently wide that wave energy is not lost out of the guide at the edges of the plates, and for this reason the H-guide is known as an open guide. Also, the spacers 12 at the edges of the strips do not affect the transmission and may be formed of either insulating or conductive material.

The two H-guide sections 10 and 11 are coupled together through a coupling aperture formed in aperture plate 14 at the middle thereof. This coupling aperture comprises an elongated slot 17 formed transversely of the axis of the H-guide sections, and preferably has rounded ends. The thickness of the aperture plate 14 is not especially critical, except that it is preferred to use a plate having a thickness less than inch. The length of the slot (parallel with the longitudinal axis of the junction) is of the order of one Wavelength at the mid-band frequency.

In order to prevent propagation in the coupling region of higher modes having three half-sinusoidal variations from the inner face of plate 10c to the inner face of plate 11c, at the location of the coupling slot 17, shoulders 10c" and 110" are provided on the inner faces of the plates in order to reduce the height or separation between plates to a value approximately equal to one and onehalf times the free space wavelength at the highest frequency of operation. This construction is illustrated in FIGURE 2 which shows a section of FIGURE 1 taken along the line 22 on an enlarged scale.

For the purpose of illustration only, a specific example of the hybrid junction will be described for use over a frequency band of 25 kmc./s. to 32 kmc./s. The two conducting plates of each H-guide section are 4 inches in width, and the polyfoam strip separating the two plates has a thickness of 0.280, and a width of 0.840", and the coupling slot 17 has a length of 0.40". The specific dimensions of different elements will vary according to the particular Waveband involved.

We claim:

1. An H-guide hybrid junction comprising two sections of waveguide of the H-type arranged in parallel relation and having a common wall over a linear section at the middle thereof, each H-guide being formed of parallel conductive plates separated by a strip of dielectric material extending throughout the length of the plates along the longitudinal center of the plates, said common wall having a coupling aperture formed therein comprising an elongated slot formed transversely of the longitudinal axis of the junction and extending beyond the edges of said dielectric strips to points near the edges of said conductive plates.

2. An H-guide hybrid junction according to claim 1 wherein the outer conductive plates positioned on opposite sides of said coupling aperture are enlarged over substantially the length of the aperture to provide inwardly extending shoulders which reduce the effective height of the guide over the region covered by the coupling aperture.

3. An H-guicle hybrid junction according to claim 2 wherein the length of said coupling aperture parallel with the longitudinal axis of the junction is of the order of one wavelength at mid-band frequency, and the height of the guide in the region covered by the coupling aperture is approximately equal to one and one-half times the free space wavelength at the highest frequency of operation.

4. An H-guide hybrid junction according to claim 1 wherein each pair of adjacent ends of the two H-guide 4; sections are spaced apart and are held in spaced relation by a common coupling flange.

References Cited by the Examiner UNITED STATES PATENTS 2,573,746 11/1951 Watson et al. 333-40 3,175,171 3/1965 Reindel 33310 A. R. MORGANSTERN, P. L. GENSLER,

Assistant Examiners. 

1. AN H-GUIDE HYBRID JUNCTION COMPRISING TWO SECTIONS OF WAVEGUIDE OF THE H-TYPE ARRANGED IN PARALLEL RELATION AND HAVING A COMMON WALL OVER A LINEAR SECTION AT THE MIDDLE THEREOF, EACH H-GUIDE BEING FORMED OF PARALLEL CONDUCTIVE PLATES SEPARATED BY A STRIP OF DIELECTRIC MATERIAL EXTENDING THROUGHOUT THE LENGTH OF THE PLATES ALONG THE LONGITUDINAL CENTER OF THE PLATES, SAID COMMON WALL HAVING A COUPLING APERTURE FORMED THEREIN COMPRISING 